The open letter makes one central point: that the SA article is a nearly pure ad hominem, i.e. that Lemore attacks E.O. Wilson himself, not any particular thing which he actually did or said. She simply does not establish anything that could be on any list (secret or otherwise) of things for which one could attack Wilson. (Just to be clear, the open letter does not make the point you impute to it – that the article makes supportable claims, but that those claims shouldn't be made against Wilson because he's a "prominent dead scientist".)

Given that, it's not as if there's any real charge of racism laid that would require a defence, and in fact the open letter does not use Wilson's environmentalism as a defence of this sort. Why then do you mention it in this connexion? Perhaps to introduce the 'motif' you mention, which despite being in quotation marks does not appear to be a direct quote.

What then, seeing as you have raised it, was the ideological content of Wilson's views on ecology and overpopulation? That population growth drives overexploitation of nature, with disastrous ecological consequences. This is opposed by those who view industry, not people, as the prime cause of overexploitation. The debate is roughly between those who would set aside and protect part of the Earth and those who see the Earth as already unnatural. Or "Half-Earth" vs. "the Anthropocene", to use each side's slogans. To be sure, some of the side opposed to Wilson have been known to attempt to racialise the views of the set-asiders. For an eloquent defence of Half-Earth against these and other ideological attacks, see "Half the earth for people (or more)? Addressing ethical questions in conservation" by Helen Kopnina. (PDF: https://scholarlypublications.universiteitleiden.nl/access/i...)

I suppose it took you five minutes or less to write your comment. That it took me half an hour to compose a sufficient reply is a fine demonstration of Brandolini's law, should any more such be needed. Just one more thing. E.O. Wilson's own words on whether population control should be imposed by anyone, on anyone:

"Should nations have a population policy? Should religions have a population policy? It seems to me that one is scurrying on the edge of fascistic ideas if one tells people how many children they can have, altering the entire nature of the society." From his interview at http://churchandstate.org.uk/2019/09/e-o-wilson-runaway-popu...